514 Wisconsin Academy of Sciences, Arts , and Letters. 
ences in the species which make np the bulk of the vegetation. 
This is evident from a glance at table 5. 
In the deepest waters in which plants are found, a different situ¬ 
ation exists. Here the flora is made up of relatively few species 
uniformly distributed, but it is characterized by the occurrence 
of luxuriant growths of Potamogeton amplifolius in more or less 
scattered patches. In this zone, as in the shallowest zone, there 
are several places where the vegetation is extremely scanty, com¬ 
posed of Najas or Potamogeton zosterifolius in very small quanti¬ 
ties. 
The Depth of each Species. The abundance of several species 
has a definite relation to the depth of water (table 9). Most of 
Potamogeton zosterifolius is found in water deeper than 3 meters, 
while P. lucens and Ranunculus are entirely limited to shallow 
water. About 75 per cent, of the Ceratophyllum and Myriophyl- 
lum of the lake is found in water from 1 meter to 3 meters deep. 
Almost exactly half of the Vallisneria is also found within the 
same limits, and since this plant forms a high percentage of the 
total yield of each zone (table 8), it is evident that this zone ex¬ 
ceeds the other two in total yield. 
Several species are limited either to the first, or to the first two 
zones, so that a smaller number of species is present in the third 
zone. Most of the species, however, show no definite depth limi¬ 
tations in their occurrence, but grow more abundantly at certain 
depths than at others. 
Comparison between Different Types of Bottom. In tables 4 
and 5 are shown the relative amounts of each species found on 
each type of lake bottom. Since the classification of the bottom 
into the two types, “sandy’’ and “muddy”, is very approximate, 
these figures have not an exact significance, but they may serve 
to indicate the kind of soil on which each species flourishes. In 
order to classify the plants according to the type of bottom on 
which they are most abundant, it is necessary to keep in mind 
their relative abundance in the different depth zones (table 9). 
Thus, in table 5 (zone 2), Potamogeton pectinatus is represented 
as occurring in about equal quantities on both types of soil, 
whereas in table 4 (zone 1), about 80 per cent, of this plant is 
found in sandy regions. Reference to table 9 shows that 75 per 
cent, of this species is found in zone 1. Hence, P, pectinatus may 
be classified as flourishing on a sandy substratum. In this way 
